JP2018152599A - Capacitors - Google Patents

Abstract

A capacitor for use in a power semiconductor capable of suppressing device breakdown due to creeping discharge is provided. A substrate, a capacitor forming region having one or more trenches in the substrate, a dummy region located between the capacitor forming region and an end of the substrate, and at least a capacitor. A first electrode and a dielectric film provided in one or more trenches to cover the formation region, a capacitor formation region, a second electrode 305 having a potential different from that of the first electrode, and a dummy region And an extension portion that is concave or convex with respect to the substrate in a path from the second electrode to the end portion of the substrate. [Selection] Figure 1

Description

  The present invention relates to a capacitor.

In recent years, semiconductor devices using trench capacitors have become widespread.
Patent Document 1 discloses a power semiconductor including a trench capacitor. The power semiconductor described in Patent Literature 1 includes a free-wheeling diode that operates equivalent to a unipolar operation, and a semiconductor circuit having a capacitor and a resistor connected in parallel to the free-wheeling diode. This semiconductor circuit functions as at least a part of the resistor. Further, the semiconductor circuit has a semiconductor substrate having a resistance value at least larger than a resistance value included in the freewheeling diode, and the semiconductor substrate as one electrode of the capacitor. And a dielectric region provided with a larger surface area.

JP 2014-241434 A

The upper electrode of the trench capacitor described in Patent Document 1 is formed in the same area as the element area in a plan view (when viewed from the upper surface of the trench). Then, in the side surface portion of the element, the upper electrode and the lower electrode (n-Si corresponds to the lower electrode in Patent Document 1) are separated by a distance corresponding to the film thickness of SiO ₂ that is a dielectric. Become. Here, the dielectric breakdown field strength of SiO ₂ is about 10 MV / cm, whereas the breakdown field strength of air is about 30 kV / cm, which is low. Since the film thickness of the capacitor dielectric such as SiO ₂ is about several μm at the maximum, for example, when a high voltage is applied between the electrodes of the trench capacitor in the power semiconductor as in Patent Document 1, the SiO ₂ Before dielectric breakdown occurs, so-called creeping discharge occurs between the upper and lower electrodes, causing not only the capacitor to fail but also the power semiconductor.

  This invention is made | formed in view of such a situation, and it aims at suppressing the apparatus destruction by creeping discharge in the capacitor used for a semiconductor for electric power.

  A capacitor according to an aspect of the present invention includes a substrate, a capacitor formation region in which one or more trenches are provided in the substrate, a dummy region located between the capacitor formation region and an end of the substrate in the substrate, A first electrode and a dielectric film provided so as to cover at least the capacitor forming region and in one or more trenches; a second electrode covering the capacitor forming region and having a potential different from that of the first electrode; and a dummy An extension formed in the region and having a concave or convex shape with respect to the substrate in a path from the second electrode to the end of the substrate.

  According to the present invention, in a power semiconductor using a trench capacitor, device breakdown due to creeping discharge can be suppressed.

1 is a plan view schematically showing the structure of a capacitor 1 according to a first embodiment of the present invention. It is AA 'sectional drawing of FIG. It is an excerpt sectional drawing which shows a mode when creeping discharge generate | occur | produces in the capacitor 1 which concerns on 1st Embodiment of this invention. It is BB 'sectional drawing of FIG. It is sectional drawing which shows roughly the structure of the capacitor 1 which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows roughly the structure of the capacitor 1 which concerns on 3rd Embodiment of this invention. It is a top view which shows roughly the structure of the capacitor 1 which concerns on 4th Embodiment of this invention. It is a top view which shows roughly the structure of the capacitor 1 which concerns on 5th Embodiment of this invention. It is sectional drawing which shows schematically the structure of the capacitor 1 which concerns on other embodiment of this invention.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

(1. Planar structure of capacitor)
FIG. 1 is a plan view of a capacitor 1 according to the present embodiment. A planar structure of the capacitor 1 will be described with reference to FIG. In FIG. 1, a configuration necessary for explaining at least a part of the features in the planar structure of the capacitor 1 is extracted and described, but the features in the planar structure of the capacitor 1 are illustrated in other drawings. It does not preclude being identified by the configuration being made.

  As shown in FIG. 1, the capacitor 1 has a planar structure in which a substrate 301, a plurality of trenches 100 formed in the substrate 301, a plurality of dummy trenches 200 (an example of an extension portion), and a ring trench 400. And an upper electrode (an example of the first electrode or the second electrode) 305 formed on the substrate 301, a terminal 325 formed on the upper electrode 305, and the upper electrode 305. And an insulating film 306. The capacitor 1 according to the present embodiment includes the dummy trench 200 as an example of the extension, thereby extending the path length between the end of the upper electrode 305 and the end of the lower electrode 302 (see FIG. 2). Discharge can be prevented. Details will be described below.

  In the present embodiment, the substrate 301 has a rectangular shape including long sides (an example of a first side) and short sides (an example of a second side). In addition to the structure shown in FIG. 1, the substrate 301 may be provided with a structure such as a transistor, an FET, a resistor, or an inductor.

  The trench 100 is a groove or a hole provided by forming an opening in the substrate 301. In the present embodiment, the trenches 100 are formed in the vicinity of the center of the substrate 301 so as to be aligned at substantially equal intervals in four rows along the x axis and in two columns along the y axis. The opening of the trench 100 has a substantially circular shape with a diameter of about 5 μm. Note that the shape of the opening of the trench 100 is not limited to a substantially circular shape. For example, it may be a polygon such as a rectangle or a triangle. Moreover, the shape where the corner | angular of the polygon was rounded may be sufficient. Further, the number of trenches 100 may be one or more, and is not limited to the number and arrangement shown in FIG.

  The upper electrode 305 is formed so as to cover a region where the trench 100 is formed and a region adjacent to the region (a region corresponding to a region where a terminal 325 described later is formed in FIG. 1) ( In the following description, a region where the upper electrode 305 is formed is referred to as a capacitor formation region R). As shown in FIG. 1, in the present embodiment, the upper electrode 305 has a shape along the contour of the trench 100 and the terminal 325, but the shape of the upper electrode 305 is not limited to this. For example, the upper electrode 305 may have a rectangular shape that covers a region where the trench 100 is formed and a region where the terminal 325 is formed.

  The capacitor formation region R is not limited to the region where the upper electrode 305 is formed, and may refer only to the region where the plurality of trenches 100 are formed (substantially central region of the substrate 301), for example.

  The terminal 325 is a terminal for electrically connecting the upper electrode 305 to the outside of the capacitor 1. The terminal 325 has a substantially rectangular shape and is formed at a position adjacent to the row in which the plurality of trenches 100 are arranged. In FIG. 1, the terminal 325 is formed adjacent to the two trenches 100 included in the column composed of the four trenches 100 arranged along the y-axis direction. Although details will be described with reference to FIG. 4, the terminal 325 is formed on the upper electrode 305, and a part of the terminal 325 is exposed through the hole 315 formed in the insulating film 306.

  In the present embodiment, the terminal 325 is formed in a region adjacent to the region where the trench 100 is formed, but is not limited thereto. For example, the terminal 325 may be formed in a region between four trenches 100 adjacent to each other (between the rows and / or columns of the trenches 100) of the plurality of trenches 100, and above the trenches 100, The trench 100 may be formed so as to cover the upper electrode 305. However, as shown in the present embodiment, the terminal 325 is formed so as not to cover the trench 100, so that the capacitor formed in the trench 100 is deteriorated or destroyed in the process of testing or mounting the capacitor 1. Can be suppressed.

  The ring trench 400 is a frame-shaped trench formed in the substrate 301 in a region where the terminal 325 is formed. The width of the opening of the ring trench 400 is preferably about 10 μm or less, for example. The ring trench 400 is not limited to a frame shape as long as it is annular, and may be annular, for example.

  The hole 315 is an opening formed by removing a part of the insulating film 306 over the terminal 325, and has a shape along the ring trench 400.

  The dummy trench 200 is a groove or a hole provided by forming an opening in the substrate 301. In the present embodiment, the plurality of dummy trenches 200 are formed in a region (an example of a dummy region) between the capacitor formation region R and the end portion of the substrate 301.

  More specifically, five dummy trenches 200 are provided at substantially equal intervals so as to be aligned on a straight line in the direction from the capacitor formation region R toward the end of the substrate 301 (the y-axis direction in FIG. 1). It has been. Further, in the present embodiment, the dummy trench 200 is formed in a region having a shorter distance among the distance a from the end of the upper electrode 305 to the long side of the substrate 301 and the distance b to the short side. . In the example of FIG. 1, the distance a is shorter than the distance b. Therefore, in the capacitor 1 according to the present embodiment, the dummy trench 200 is directed to the upper electrode 305 and the longer side of the substrate 301 (the y-axis direction in FIG. 1; hereinafter, also referred to as “first direction”). Are arranged between the long side of the substrate 301 and the capacitor formation region R. Note that the capacitor 1 has a configuration in which the dummy trench 200 is formed in both the region between the capacitor formation region R and the long side and the region between the short side and the region between the short side. It is also possible to adopt a configuration formed in the above.

  The shape of the opening of the dummy trench 200 is substantially rectangular (an example of an opening having a longitudinal direction). Specifically, the opening of the dummy trench 200 has a longitudinal direction that is substantially perpendicular to the first direction (y-axis direction in FIG. 1) (the x-axis direction in FIG. 1; hereinafter, “second direction”). Also called). The shape of the opening of the dummy trench 200 is not limited to a substantially rectangular shape. For example, it may be a polygon such as a rectangle or a triangle, or a circle. Moreover, the shape where the corner | angular of the polygon was rounded may be sufficient. Furthermore, the number of dummy trenches 200 may be one or more, and is not limited to the number shown in FIG.

(2. Cross-sectional structure of capacitor)
A cross-sectional structure of the capacitor 1 will be described with reference to FIG. FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG. 1 and schematically showing a configuration example of the capacitor 1 according to the first embodiment of the present invention. As shown in FIG. 2, the capacitor 1 includes a substrate 301, a lower electrode 302, a dielectric film 303, a buffer film 304, an upper electrode 305, and an insulating film 306.

The substrate 301 is made of, for example, Si (silicon) having a thickness of about 680 μm. Note that when the substrate 301 is formed of n-type Si (silicon) or p-type Si, the substrate 301 can also function as a lower electrode 302 described later. In this case, P (phosphorus), As (arsenic), Sb (antimony), or the like can be included as an n-type dopant. As a p-type dopant, B (boron) etc. can be included.
A plurality of trenches 100 and a plurality of dummy trenches 200 are formed in the substrate 301.

  The plurality of trenches 100 are grooves formed in the thickness direction of the substrate 301. The trench 100 is formed by, for example, dry etching. The depth of the trench 100 is preferably about 15 μm to 25 μm, for example. Note that the depth of the trench 100 refers to a distance from a plane extending along the surface of the substrate 301 in the trench 100 to a point farthest from the plane in the trench 100.

  Similar to the trench 100, the plurality of dummy trenches 200 are grooves formed in the thickness direction of the substrate 301. The dummy trench 200 is formed by, for example, dry etching. Details of the cross-sectional structure of the dummy trench 200 will be described later.

  A lower electrode 302 (which is an example of a first electrode or a second electrode) is formed on the surface of the substrate 301 including the inner wall of the trench 100 and the inner wall of the dummy trench 200. The lower electrode 302 is formed using, for example, Mo (molybdenum), Al (aluminum), Au (gold), W (tungsten), Pt (platinum), or the like. The material of the lower electrode 302 is not limited to a metal as long as it is a conductive material, and may be a conductive resin, for example. The lower electrode 302 only needs to be formed at least in the capacitor formation region R, and may not be formed in other regions (for example, the inner wall of the dummy trench 200) on the surface of the substrate 301.

An oxide film (not shown) having a thickness of about 0.3 μm is preferably formed between the substrate 301 and the lower electrode 302 by being oxidized by a technique such as thermal oxidation. The oxide film is also formed on the inner wall of the trench 100 and the inner wall of the dummy trench 200. The oxide film is formed from silicon oxide (for example, SiO ₂ ) or the like. By forming the oxide film on the surface of the substrate 301, the resistance of the capacitor formed in the trench 100 can be improved.

  A dielectric film 303 having a thickness of about 1 μm is formed on the surface of the lower electrode 302 including the inner wall of the trench 100 and the inner wall of the dummy trench 200. The dielectric film 303 is made of silicon nitride (for example, Si3N4). The dielectric film 303 may be formed so as to cover at least the capacitor formation region R, and may not be formed in other regions on the surface of the substrate 301 (for example, the inner wall of the dummy trench 200). .

  Further, in the capacitor forming region R, an upper electrode 305 having a thickness of about 4 μm is formed on the surface of the dielectric film 303 including the inner wall of the trench 100 via a buffer film 304 having a thickness of about 0.5 μm. The buffer film 304 is formed using a conductive material such as doped polycrystalline Si (polysilicon).

  After the buffer film 304 is stacked on the dielectric film 303, the buffer film 304 is removed from the region other than the surface of the capacitor formation region R by etching or the like. However, in this embodiment, the buffer film 304 inside the trench 100 and the dummy trench 200 remains without being removed. It is preferable that the buffer film 304 is completely removed from the viewpoint of making creeping discharge difficult to occur. Even when the material for forming the upper electrode 305 is difficult to adhere to the material for forming the dielectric film 303, the adhesion can be improved by sandwiching the buffer film 304 therebetween.

  The upper electrode 305 is formed using, for example, Mo (molybdenum), Al (aluminum), Au (gold), W (tungsten), Pt (platinum), or the like. The material of the upper electrode 305 is not limited to a metal as long as it is a conductive material, and may be, for example, a conductive resin. When the lower electrode 302 is formed only in the capacitor formation region R, the upper electrode 305 may be formed in a region other than the capacitor formation region R (for example, the inner wall of the dummy trench 200). Further, as shown in FIG. 2, the surface of the upper electrode 305 has a depression at a position corresponding to the opening of the trench 100.

  Thus, the capacitor formation region R functions as a capacitor by including a laminated structure of the lower electrode 302, the dielectric film 303, and the upper electrode 305. Note that, as described above, in the case where silicon or the like whose resistance is reduced is used for the substrate 301, the substrate 301 can also function as the lower electrode 302.

  An insulating film 306 having a thickness of about 30 μm is formed on the outermost surface of the capacitor 1 including the inner walls of the dummy trench 200 and the trench 100. The insulating film 306 is formed using, for example, polyimide. The surface of the insulating film 306 has depressions at positions corresponding to the openings of the dummy trench 200 and the trench 100. The insulating film 306 covers the surface of the capacitor 1, at least one dummy trench 200 and at least one trench 100, and extends from at least the capacitor formation region R to the region where the dummy trench 200 is formed (dummy region). However, the present invention is not limited to a configuration that covers substantially the entire surface of the substrate 301.

  Next, the cross-sectional structure of the dummy trench 200 will be described in detail. In the present embodiment, among the plurality of dummy trenches 200, the dummy trench 200 formed in the vicinity of the boundary with the capacitor formation region R is deeper than the other dummy trenches 200 and extends along the first direction of the opening. The length is preferably large. More preferably, as it approaches the vicinity of the boundary of the capacitor forming region R, the groove of the formed dummy trench 200 is gradually deepened, and the length of the opening along the first direction is gradually increased.

  The depth of the dummy trench 200 is preferably not less than 0.5 times and not more than twice the depth of the trench 100, for example. The depth of the dummy trench 200 refers to a distance from a plane extending along the surface of the substrate 301 at the opening of the dummy trench 200 to a point farthest from the plane inside the dummy trench 200. The dummy trench 200 preferably has a longitudinal diameter of the opening (a length along the x-axis direction in FIG. 1) longer than a width of the upper electrode 305 provided substantially parallel to the longitudinal direction. . Specifically, the opening of the dummy trench 200 preferably has a length along the first direction of 1 μm or more and 100 μm or less.

  Since the capacitor formation region R where the upper electrode 305 is formed has a larger thermal expansion coefficient than other regions where the upper electrode 305 is not provided, stress is concentrated near the boundary between the capacitor formation region R and the other regions. End up. In the capacitor 1 according to the present embodiment, stress concentration due to the upper electrode 305 can be prevented by deepening the groove of the dummy trench 200 formed near the boundary of the capacitor formation region R.

  Further, by reducing the length along the first direction of the opening of the dummy trench 200 formed outside the vicinity of the boundary with the capacitor formation region R, it becomes possible to form more dummy trenches 200. .

(3. Function of dummy trench)
Next, the function of the dummy trench 200 in the capacitor 1 according to the present embodiment will be described with reference to FIG. FIG. 3 is an enlarged view of a part of the cross-sectional view (FIG. 2) of the capacitor 1 according to the present embodiment. For example, when the capacitor 1 is used in a device that is driven at a high voltage such as a power semiconductor device, a strong electric field is also applied to the capacitor 1. As a result, creeping discharge may occur in the capacitor 1 due to electric field concentration. The starting point of the creeping discharge is, for example, the points P1 to P3 circled in FIG.

  A point P1 indicates a contact portion (triple junction) of three elements of the insulating film 306, the upper electrode 305, and the buffer film 304. Triple junctions tend to cause electric field concentration due to large distortion of the electric field. Therefore, it can be a starting point for creeping discharge.

  A point P <b> 2 is a corner portion of the upper electrode 305 and is a contact portion between the upper electrode 305 and the insulating film 306. The point P3 is a corner portion of the upper electrode 305, and is a contact portion between the upper electrode 305 and the buffer film 304. The distortion of the electric field also increases at the corners of the conductor (the upper electrode 305 in this embodiment) and the contact portion between the conductor and the insulator (the insulating film 306 in this embodiment). Therefore, the points P2 and P3 can also be a starting point of creeping discharge.

  For example, the charges generated at the points P1 to P3 travel along the boundary between the insulating film 306 and the dielectric film 303 (or the buffer film 304) or the surface of the insulating film 306 as schematically shown by arrows in FIG. , And propagates in the direction from the points P1 to P3 toward the end of the substrate 301 (hereinafter, the path through which the generated charges propagate to the end of the substrate 301 is referred to as “charge path”). The electric charge traveling along this boundary causes secondary avalanche and gradually expands. When the swollen charges reach the end of the substrate 301, there is a possibility of causing element breakdown (for example, dielectric breakdown).

  The starting point of the creeping discharge is not limited to the points P1 to P3 as long as the electric field concentrates at any location.

  In the capacitor 1 according to the present embodiment, by providing the dummy trench 200 between the capacitor forming region R and the end of the substrate 301, the charge path from the start point of creeping discharge to the end of the substrate 301 is extended. Can do. As a result, it becomes possible to prevent the charge that has caused avalanche of secondary electrons from reaching the end portion of the substrate 301 and to suppress element breakdown.

  Furthermore, in the present embodiment, the dummy trench 200 has a distance (a, b) from the capacitor formation region R to the end of the substrate 301 in the region between the capacitor formation region R and the end of the substrate 301. It is formed in the shorter region. The creeping discharge voltage is lower when the distance (a, b) from the capacitor formation region R to the end of the substrate 301 is shorter. Therefore, by forming the dummy trench 200 in a region where the distance (a, b) from the capacitor formation region R to the end of the substrate 301 is shorter (in this embodiment, the region on the long side of the substrate 301), The creeping discharge resistance can be improved more effectively.

  Furthermore, in the present embodiment, the surface of the insulating film 306 has a depression at a position corresponding to the opening of the dummy trench 200. Thus, even when charges pass through the surface of the insulating film 306, the charge path can be extended. Further, since the depression is formed on the surface of the insulating film 306 by forming the dummy trench 200, it is not necessary to cut the surface of the insulating film 306 to form a depression, and the number of processes can be reduced.

  The capacitor 1 may be configured to include a guard ring between the upper electrode 305 and the end of the substrate 301. In the guard ring formed using an insulating film, the distance between the upper electrode 305 and the substrate 301 can be increased, so that creeping discharge can be reduced. Further, in the guard ring by the injection layer formed by adding impurities in the vicinity of the end portion of the substrate 301, the electric field applied to the capacitor 1 can be reduced because the electric field at the end portion of the substrate 301 is relaxed. Creeping discharge can be further reduced.

(4. Function of ring trench)
Next, the configuration and function of the ring trench 400 will be described in detail with reference to FIG. FIG. 4 is an extracted part of the BB ′ cross section of FIG.

  As shown in FIG. 4, the ring trench 400 is formed adjacent to a region where the trench 100 is formed. The ring trench 400 is preferably shallower than the dummy trench 200 and the trench 100. The ring trench 400 can be formed in the same process as the trench 100 and the dummy trench 200 by etching or the like. For example, the ring trench 400 is formed by making the opening diameter in etching smaller than the opening diameter when the trench 100 is formed.

  Similar to the trench 100 and the dummy trench 200, the lower electrode 302, the dielectric film 303, and the buffer film 304 are formed on the inner wall of the ring trench 400, and the opening of the ring trench 400 is filled through the buffer film 304. The upper electrode 305 is laminated on the substrate. As a result, the surface of the upper electrode 305 has a depression at a position corresponding to the opening of the ring trench 400.

  The terminal 325 is formed on the upper electrode 305 provided in the region where the ring trench 400 is formed. The terminal 325 is formed using, for example, Mo (molybdenum), Al (aluminum), Au (gold), W (tungsten), Pt (platinum), or the like, similar to the upper electrode 305. The material of the terminal 325 is not limited to metal as long as it is a conductive material, and may be a conductive resin, for example.

  The surface of the terminal 325 formed on the ring trench 400 has a depression at a position corresponding to the opening of the ring trench 400. Note that the recess is formed along the periphery of the terminal 325 in a plan view. Accordingly, the terminal 325 has a cross-sectional shape that rises from a depression formed in the peripheral edge toward the center of the terminal 325.

  In addition, the insulating film 306 formed so as to cover the upper electrode 305 and the terminal 325 has an opening (hole 315) from which a part thereof is removed in a substantially central region of the terminal 325. The insulating film 306 is provided so as to cover a part of the peripheral edge portion (that is, the depression) of the terminal 325 by forming a hole 315 in the approximate center of the terminal 325.

  In FIG. 4, the end of the insulating film 306 on the hole 315 side is located near the deepest position in the depression of the terminal 325, more specifically, slightly closer to the center of the terminal 325 than the deepest position of the depression. doing. The end of the insulating film 306 on the hole 315 side is preferably provided at the deepest position in the depression of the terminal 325, but may be provided at a position near the center of the terminal 325 or the end of the terminal 325. . Note that the deepest position of the depression of the terminal 325 refers to a point farthest from the plane in the depression from a plane extending along the central portion of the terminal 325 on the depression.

  Furthermore, the end portion of the insulating film 306 on the hole 315 side is preferably formed such that an angle θ formed between the end portion and the vertical direction is 0 degree or more and less than 90 degrees.

  An effect obtained by forming the insulating film 306 in the above-described shape over the terminal 325 will be described. In FIG. 4, a point P4 is a contact portion between the insulating film 306 and the terminal 325, and shows a triple junction of three elements of the insulating film 306, the terminal 325, and the vacuum region (outside of the capacitor 1). When the insulating film 306 is formed so as to cover a part of the depression of the terminal 325, a difference in height may be caused between the central portion (vertex) of the terminal 325 and the connection portion between the terminal 325 and the insulating film 306. it can. Thus, the insulating film 306 functions as a shield for triple junctions such as the point P4. That is, by causing a height difference in the connection portion between the terminal 325 and the insulating film 306, the creeping discharge voltage at the triple junction increases, so that the occurrence of creeping discharge can be suppressed. Furthermore, as the angle θ becomes sharper, the side surface of the insulating film 306 on the hole 315 side becomes closer to the raised portion of the terminal 325. As a result, the creeping discharge voltage can be further increased, and the occurrence of creeping discharge can be suppressed.

[Second Embodiment]
In the second and subsequent embodiments, description of matters common to the first embodiment is omitted, and only different points will be described. In particular, the same operation effect by the same configuration will not be sequentially described for each embodiment.

  FIG. 5 is a cross-sectional view illustrating a configuration example of the capacitor 1 according to the present embodiment. In addition, the same code | symbol is attached | subjected to the structure equivalent to the capacitor 1 shown in FIG. 2, and description is abbreviate | omitted.

  As shown in FIG. 5, the capacitor 1 according to the present embodiment includes a dummy trench 201 instead of the dummy trench 200 in the first embodiment.

  In the present embodiment, among the plurality of dummy trenches 201, the dummy trench 201 formed in the vicinity of the end portion of the substrate 301 has a deeper groove than the other dummy trenches 201 and is long along the first direction of the opening. Is preferably large. More preferably, as the vicinity of the end portion of the substrate 301 is approached, the groove of the formed dummy trench is gradually deepened, and the length of the opening along the first direction is gradually increased.

In the manufacturing process of the capacitor 1, when a plurality of capacitors 1 are formed on the wafer and the capacitor 301 is obtained by dicing the substrate 301, stress is applied to the end portion (dicing line) of the substrate 301. The capacitor 1 according to this embodiment can reduce the stress applied to the substrate 301 during dicing by providing the dummy trench 201 with a deep groove in the vicinity of the end of the substrate 301.
Other configurations and effects are the same as those of the first embodiment.

[Third Embodiment]
FIG. 6 is a cross-sectional view illustrating a configuration example of the capacitor 1 according to the present embodiment. In addition, the same code | symbol is attached | subjected to the structure equivalent to the capacitor 1 shown in FIG. 2, and description is abbreviate | omitted.

  As shown in FIG. 6, the capacitor 1 according to this embodiment includes a dummy trench 202 instead of the dummy trench 200 in the first embodiment.

In the present embodiment, among the plurality of dummy trenches 202, the dummy trench 202 formed in the vicinity of the boundary with the region R1 and the dummy trench 202 formed in the vicinity of the end of the substrate 301 are more than the other dummy trenches 202. However, it is preferable that the groove is deep and the length of the opening along the first direction is large. More preferably, among the plurality of dummy trenches 202 arranged along the first direction, the central dummy trench 202 has the shallowest groove, and the length of the opening along the first direction is small. From there, as the vicinity of the end of the substrate 301 is approached, and as the vicinity of the boundary of the region R1 is approached, the groove of the formed dummy trench 202 is gradually deeper and the length of the opening along the first direction is increased. Gradually grows.
Other configurations and effects are the same as those in the first embodiment and the second embodiment.

[Fourth Embodiment]
FIG. 7 is a plan view illustrating a configuration example of the capacitor 1 according to the present embodiment. In addition, the same code | symbol is attached | subjected to the structure equivalent to the capacitor 1 shown in FIG.1 and FIG.2, and description is abbreviate | omitted.

  In the present embodiment, the capacitor 1 includes a trench 101 and a dummy trench 203 instead of the configuration of the trench 100 and the dummy trench 200 in the first embodiment.

  As shown in FIG. 7, the trench 101 has an elliptical shape having a longitudinal direction in the direction along the x-axis. In addition, the trenches 101 are formed in only one row in the direction along the x-axis direction. The other configuration of the trench 101 is the same as the configuration of the trench 100 in the first embodiment.

  Similar to the upper electrode 305 in the first embodiment, the upper electrode 305 according to the present embodiment has a shape along the contours of the trench 101 and the terminal 325. That is, the upper electrode 305 according to the present embodiment has a position corresponding to a contact point between the minor axis and the circumference of the trench 101 in the outer edge of the upper electrode 305 (that is, the outer edge of the upper electrode 305 and the minor axis of the trench 101). In the extension line and the contact), the distance from the end of the substrate 301 is designed to be the shortest.

  Next, the dummy trench 203 according to the present embodiment is designed such that the diameter of the opening in the longitudinal direction (the length along the x-axis direction in FIG. 7) is smaller than the major diameter of the trench 101 along the x-axis direction. Has been. The dummy trench 203 is formed only in a region where the distance between the end of the upper electrode 305 and the end of the substrate 301 is short. That is, the dummy trench 203 is formed so as to cover at least a position in the upper electrode 305 corresponding to the contact point between the minor axis of the trench 101 and the circumference.

  As described above, in this embodiment, since the length of the dummy trench 203 in the longitudinal direction is formed smaller than the major axis of the trench 101, for example, creeping discharge is generated even when the layout on the substrate 301 has no margin. Sufficient dummy trenches to be reduced can be provided in accordance with the layout. In other words, the degree of freedom of layout of elements, wirings, and the like in the substrate 301 can be improved.

In FIG. 7, a dummy trench is not formed in a region between the terminal 325 and the end portion of the substrate 301, but a configuration in which a dummy trench is also formed in the region may be employed.
Other configurations and effects are the same as those of the first embodiment.

[Fifth Embodiment]
FIG. 8 is a plan view illustrating a configuration example of the capacitor 1 according to the present embodiment. In addition, the same code | symbol is attached | subjected to the structure equivalent to the capacitor 1 shown in FIG.1 and FIG.2, and description is abbreviate | omitted.

  As shown in FIG. 8, the substrate 301 according to this embodiment includes a trench 102 instead of the trench 100.

The opening of the trench 102 has a substantially rectangular shape whose diameter along the second direction is longer than the diameter along the first direction. Note that the shape of the opening of the trench 102 is not limited to a substantially rectangular shape, and may be, for example, an elliptical shape. In addition, the number of the trenches 102 provided side by side in the first direction and / or the second direction is also arbitrary.
Other configurations and effects are the same as those in the first and second embodiments.

  The exemplary embodiments of the present invention have been described above. A capacitor 1 according to an embodiment of the present invention includes a substrate 301, a capacitor formation region R in which one or more trenches 100 are provided in the substrate 301, and an end of the capacitor formation region R and the substrate 301. And a first electrode provided in the one or more trenches 100 so as to cover at least the capacitor forming region R and the dummy region in which the one or more dummy trenches 200 are formed. (For example, the lower electrode 302), the dielectric film 303, the second electrode (for example, the upper electrode 305) provided inside the one or more trenches 100 so as to cover the capacitor forming region R, and the capacitor forming region R To at least one of the one or more trenches 100 and at least one of the one or more dummy trenches 200. It includes an insulating film 306 provided so as to cover the. Thereby, the capacitor 1 according to the position embodiment of the present invention can extend the charge path from the start point of the creeping discharge to the end of the substrate 301. Therefore, in the capacitor 1, it becomes possible to prevent the charge that has caused the avalanche of secondary electrons from reaching the end portion of the substrate 301, and element breakdown can be suppressed.

  Further, it is preferable that the one or more dummy trenches 200 include a plurality of dummy trenches 200 and are arranged in a first direction from the capacitor formation region R toward the end of the substrate 301. Each of the one or more dummy trenches 200 preferably has an opening having a longitudinal direction, and the longitudinal direction is preferably along a second direction substantially perpendicular to the first direction. Further, the upper electrode 305 has a predetermined width in the longitudinal direction, and the one or more dummy trenches 200 have an opening having a longitudinal diameter larger than the predetermined width of the upper electrode 305. preferable. As a result, the capacitor 1 can enhance the creeping discharge characteristics.

  Further, the substrate 301 has a rectangular shape having a first side and a second side perpendicular to the first side, and the one or more dummy trenches 200 are provided between the capacitor formation region R and the first side. The distance from the capacitor formation region R to the first side of the substrate 301 is preferably shorter than the distance from the capacitor formation region R to the second side of the substrate 301. Thus, by providing the dummy trench 200 only in the region where the distance to the end of the substrate 301 is short, the creeping discharge characteristics can be enhanced even when the layout of the capacitor 1 has no margin.

  The surface of the insulating film 306 preferably has a depression at a position corresponding to the opening of one or more dummy trenches 200. Thus, even when charges pass through the surface of the insulating film 306, the charge path can be extended.

Further, the one or more dummy trenches 200 include a dummy trench 200 provided near the boundary of the capacitor formation region R and a dummy trench 200 formed outside the vicinity of the boundary, and are provided near the boundary of the capacitor formation region R. The dummy trench 200 is preferably deeper than the dummy trench formed outside the vicinity of the boundary. The one or more dummy trenches 200 include a dummy trench 200 provided near the boundary of the capacitor formation region R and a dummy trench 200 formed outside the boundary, and are provided near the boundary of the capacitor formation region R. It is preferable that the length of the dummy trench 200 along the first direction of the opening is larger than the dummy trench 200 provided outside the vicinity of the boundary. In the capacitor 1 according to the embodiment of the present invention, stress concentration due to the upper electrode 305 can be prevented by deepening the groove of the dummy trench 200 formed near the boundary of the capacitor formation region R. Furthermore, by reducing the length along the first direction of the opening of the dummy trench 200 formed outside the vicinity of the boundary with the capacitor formation region R, more dummy trenches 200 can be formed. .

  The one or more dummy trenches 200 include a dummy trench 200 provided in the vicinity of the end portion of the substrate 301 and a dummy trench 200 formed in a portion other than the vicinity of the end portion, and a dummy provided in the vicinity of the end portion of the substrate 301. It is preferable that the trench 200 is deeper than the dummy trench 200 provided outside the vicinity of the end. Further, the one or more dummy trenches 200 include a dummy trench 200 provided near the end of the substrate 301 and a dummy trench 200 formed other than in the vicinity of the end, and are provided near the end of the substrate 301. It is preferable that the length along the first direction of the opening of the dummy trench 200 is larger than that of the dummy trench 200 provided outside the vicinity of the end. In the capacitor 1 according to the embodiment of the present invention, the stress applied to the substrate 301 at the time of dicing can be reduced by providing the deep trench dummy trench 201 near the end of the substrate 301. Further, by reducing the length along the first direction of the opening of the dummy trench 200 formed outside the vicinity of the boundary with the capacitor formation region R, it becomes possible to form more dummy trenches 200. .

  Further, in the capacitor formation region R, a ring trench 400 having a ring-shaped opening provided in a region other than a region where the one or more trenches 100 are provided, and an upper electrode 305 on the ring trench 400. And a terminal 325 for electrically connecting the upper electrode 305 to the outside. The surface of the terminal 325 has a ring-shaped depression at a position corresponding to the opening of the ring trench 400. The insulating film 306 preferably has a hole formed in a ring-shaped depression. According to this preferred embodiment, the insulating film 306 is formed so as to cover a part of the depression of the terminal 325, so that the central portion (vertex) of the terminal 325 and the connection portion between the terminal 325 and the insulating film 306 are high and low. A difference can be made. Thus, the insulating film 306 functions as a triple junction shield. That is, by causing a height difference in the connection portion between the terminal 325 and the insulating film 306, the creeping discharge voltage at the triple junction increases, so that the occurrence of creeping discharge can be suppressed. Furthermore, as the angle θ becomes sharper, the side surface of the insulating film 306 on the hole 315 side becomes closer to the raised portion of the terminal 325. As a result, the creeping discharge voltage can be further increased, and the occurrence of creeping discharge can be suppressed.

  Each embodiment described above is for facilitating the understanding of the present invention, and is not intended to limit the present invention. The present invention can be changed / improved without departing from the spirit thereof, and the present invention includes equivalents thereof. In other words, those obtained by appropriately modifying the design of each embodiment by those skilled in the art are also included in the scope of the present invention as long as they include the features of the present invention. For example, each element included in each embodiment and its arrangement, material, condition, shape, size, and the like are not limited to those illustrated, and can be changed as appropriate.

For example, in the above-described embodiment, the configuration in which the capacitor 1 includes the ring trench 400 has been described. However, the present invention is not limited to this. For example, the capacitor 1 may be configured without the ring trench 400. The capacitor 1 may be configured to include the dummy trench 200 only at a position corresponding to one of the trench 100 or the ring trench 400. Further, the capacitor 1 may have a configuration in which an insulating film 306 is formed so as to be concave with respect to the substrate 301 instead of the dummy trench 200 (FIG. 9). In this case, the insulating film 306 functions as an extension portion. Further, as shown in FIG. 9, by forming irregularities on the surface of the insulating film 306, the path length from the end of the upper electrode 305 to the end of the substrate 301 can be further extended.
Each embodiment is an exemplification, and it is needless to say that a partial replacement or combination of configurations shown in different embodiments is possible, and these are also included in the scope of the present invention as long as they include the features of the present invention. .

1 Capacitor 100, 101 Trench 200, 201, 202, 203 Dummy trench 301 Substrate 302 Lower electrode 303 Dielectric film 304 Buffer film 305 Upper electrode 325 Terminal 306 Insulating film

Claims (13)

A substrate,
A capacitor forming region provided with one or more trenches in the substrate;
In the substrate, a dummy region located between the capacitor formation region and the end of the substrate,
A first electrode and a dielectric film provided so as to cover at least the capacitor formation region and inside the one or more trenches;
A second electrode that covers the capacitor formation region and has a different potential from the first electrode;
An extension formed in the dummy region, and having a concave or convex shape with respect to the substrate in the path from the second electrode to the end of the substrate;
A capacitor comprising: The extension is provided on the shortest path between the second electrodes and the end of the substrate.
The capacitor according to claim 1. The extension is
An insulating film formed so as to cover the substrate;
The capacitor according to claim 1 or 2. The extension is one or more dummy trenches formed in the thickness direction of the substrate,
The capacitor according to claim 1 or 2. The one or more dummy trenches are
An opening having a longitudinal direction, the longitudinal direction being provided along a second direction substantially perpendicular to the first direction from the capacitor formation region toward the end of the substrate;
The capacitor according to claim 4. The second electrode has a predetermined width in the longitudinal direction,
The one or more dummy trenches are
A diameter in a longitudinal direction of the opening is larger than the predetermined width of the second electrode;
The capacitor according to claim 5. The substrate has a rectangular shape having a first side and a second side perpendicular to the first side;
The one or more dummy trenches are provided between the capacitor formation region and the first side,
A distance from the capacitor formation region to the first side of the substrate is shorter than a distance from the capacitor formation region to the second side of the substrate;
The capacitor according to any one of claims 4 to 6. An insulating film extending from the capacitor formation region to the dummy region and covering at least one of the one or more trenches and at least one of the one or more dummy trenches;
In addition,
The surface of the insulating film is
Having a depression at a position corresponding to the opening of the one or more dummy trenches,
The capacitor according to any one of claims 4 to 7. The one or more dummy trenches are
Including a dummy trench provided in the vicinity of the capacitor formation region, and a dummy trench formed in a region other than the vicinity of the capacitor formation region,
The dummy trench provided in the vicinity of the capacitor formation region has a deeper groove than the dummy trench formed outside the vicinity of the capacitor formation region,
The capacitor according to any one of claims 4 to 8. The one or more dummy trenches are
Including a dummy trench provided in the vicinity of the capacitor formation region, and a dummy trench formed in a region other than the vicinity of the capacitor formation region,
The dummy trench provided in the vicinity of the capacitor formation region has a larger length along the first direction of the opening than the dummy trench provided in a region other than the vicinity of the capacitor formation region.
The capacitor according to any one of claims 4 to 9. The one or more dummy trenches are
Including a dummy trench provided near the end of the substrate, and a dummy trench formed outside the vicinity of the end,
The dummy trench provided near the end of the substrate is deeper than the dummy trench provided outside the vicinity of the end,
The capacitor according to any one of claims 4 to 10. The one or more dummy trenches are
Including a dummy trench provided near the end of the substrate, and a dummy trench formed outside the vicinity of the end,
The dummy trench provided near the end of the substrate has a length along the first direction of the opening larger than the dummy trench provided outside the vicinity of the end,
The capacitor according to any one of claims 4 to 11. A ring trench having a ring-shaped opening provided in a region other than the region in which the one or more trenches are provided in the capacitor formation region;
A terminal provided on the ring trench via the second electrode for electrically connecting the second electrode to the outside;
Further comprising
The surface of the terminal has a ring-shaped depression at a position corresponding to the opening of the ring trench,
The insulating film is
Having a hole formed in the annular recess,
The capacitor according to claim 8.

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